In smartcards, the computing time, communication bandwidth, and transient memory (RAM) are limited. In addition, writing to persistent memory is much more expensive than writing to temporary memory, and finally no assumptions about the integrity of the communications infrastructure can be made.
A problem is that systems with state information residing in a persistent memory such as EEPROM are required to ensure that this information stays consistent even in case of unexpected power losses and other failures.
A transition from one consistent system state to another may involve updates of several cells of persistent memory. These updates should be performed atomically, where either all memory cells are updated or none of them.
If power is lost or some other system failure occurs prior to the completion of the transaction-commit operation, all conditional updates are discarded.
In a resource-constrained environment, such as a smartcard, the size of a transaction buffer is highly critical. Its better to find an implementation, where a transaction buffer isn't need at all. Writing persistent memory is time-consuming compared to reading. The other goal is to reduce the number of expensive write-Operations to persistent Storage needed for transaction support.
Therefore, it is an object of the invention to provide a method and a device for Block-Oriented Memory-Management provided in Smart Card Controllers in order to avoid memory waste and time by using a transaction buffer. It is another object of the invention to have the consistency of transactional writing guaranteed using a new update method.